This invention relates to local area network (LAN) communication and specifically, to CSMA/CD communication of the type commonly used in accordance with a network standard known as Ethernet. Ethernet contemplates packet communication via a shared medium in which all stations or nodes can monitor all broadcast messages on a network. An Ethernet local area network standard has been adopted under designation IEEE 802.3. An adaptation of the standard to telephone-type wiring is the IEEE 802.3 10BaseT standard in which the medium is unshielded twisted pair wire.
There is a trade-off between the maximum network diameter, or the electrical distance between the two furthest-apart network nodes within a contiguous network sharing the same medium, and the minimum size of a message unit or packet carried on the medium of a local area net using the IEEE 802.3 standards. The 802.3 standard specifies a 10 Megabit/second (MBPS) data rate and a 51.2 microsecond (.mu.s) minimum packet length. The round-trip time across the diameter of a network must be less than the time for transmission of a packet of the minimum packet length to ensure that a station is always able to detect if a packet has collided with a packet from another node or station. Under current standards of 10 MBPS, a diameter of 2500 meters allows transmission of 512 bits in a 51.2 microsecond packet length. The maximum packet rate is therefore 14,881 packets per second. By contrast, if either the network diameter is reduced by a factor of 10 and all other performance parameters are raised by a factor of 10, for example, the unavoidable requirement that the minimum-sized packets and the round-trip time through the maximum network diameter has resulted in unacceptable combinations of minimum packet size and network diameter.
The 10BaseT adaptation of the 802.3 standard allows the physical structure to be star-wired with each station or node being connected at the tip of a star through spokes formed by a loop which is connected to a center or hub. Interconnection of the stations is at the hub such that all stations tied to a hub have the same logical connectivity as stations connected to a bus-type system. However, each link of the spoke must have a port at the hub which contains active electronics, and the hub typically must be supplied with electrical power. The hub box represents a potential common point of failure. However, since each station is connected to a separate port on the box, there is an opportunity for individual monitoring of the status of each station connection at the hub from a central location, which is a very important consideration in network management.
Hubs are also useful in that bridges can be used to isolate hub bandwidth traffic which is local to a single hub. Therefore, hubs are being used increasingly to allow physical management of the wires to a hub as well as easy logical management of the ports on the hub. Therefore, it become practical to consider network diameters considerably smaller than those specified in the Ethernet standard.
One of the areas of emerging agreement for a new standard for digital networks is the adoption of the standard media access control (MAC) protocol defined by Ethernet. On the other hand, if there is a single point to point link, full duplex communication is possible, and there is no need for a MAC.
Terminators are known for multiple-path solid media. It is believed that LAN manufacturer Synoptics has a design for such a terminator. A simple and low-cost terminator may allow the implementation of practical high-speed networks using relatively low-grade wire media.